Posted
by
Soulskill
on Friday November 18, 2011 @08:48AM
from the looking-for-mistakes dept.

gbrumfiel writes "Earlier this year, the OPERA experiment made the extraordinary claim that they had seen neutrinos traveling faster than the speed of light. The experiment, located at Gran Sasso in Italy, saw neutrinos arrive 60 nanoseconds earlier than expected from their starting point at CERN in Switzerland. Others have doubted OPERA's claim, but in a new paper, the group reaffirms its commitment to the measurement. 'It's slightly better than the previous result,' OPERA's physics coordinator Dario Autiero told Nature News. Most members of the collaboration who didn't sign the original paper out of skepticism have now come on board. But scientists outside the group still aren't sure. 'Independent checks are the way to go,' says Rob Plunkett, co-spokesman of a rival experiment called MINOS."

As others here noted last time this result came around, if neutrinos really travel that much faster than the speed of light, then we would have expected the neutrino burst from the 1987a supernova to arrive months, rather than hours, before the light came. Thus, I am skeptical.

He's not speaking religion. There's nothing metaphysical in his statement. He didn't say god wouldn't allow Neutrinos to be faster of light, or something like that. You cannot divide things just into science and religion. Some things are neither.

I am sure there are reasons why this new publication was not completely dismissed. Maybe it is not that certain that the neutrinos detected 1987 were really from that supernova, or maybe neutrinos somehow have a higher speed in matter than in the vacuum?

There have already been four credible ideas posted in this discussion as to why the measurements we are seeing could differ from prior ones, without either being wrong. Different energies, different neutron flavors, interactions with gravity, interactions with mass, etc. Neutrons are still not completely understood, and since their predictions/discovery we have had to change the standard model twice (that I am aware of) to match new observations, and we will likely have to again in light of growing evidence of flavor oscillations. Non-baryonic matter is very much at the ragged edge of what experimental physics can observe, and finding unexpected things should be expected.

I'm skeptical of their results, and think that there is probably something that hasn't been accounted for in their timing. But if you flat-out dismiss new evidence because it doesn't agree with your models based on past evidence, then you have crossed the bounds from scientific skepticism to personal belief.

His point (which should be modded up) is that God or no God, the essential difference between religion and science is that religion puts articles of faith before observed data. Which is exactly what the post he was responding to was doing.

Don't get me wrong: I think the OPERA experiment will turn out to be wrong. But neutrinos are so poorly-understood and poorly-observed that any blanket dismissal of OPERA's results counts as an act of faith.

No. He put one set of observed data before another. If he didn't have the reference to 1987a then I would agree with you. He is simply saying that these two sets of observed data seem to conflict and he believes that the data from the 1987a supernova is more reliable.

He is simply saying that these two sets of observed data seem to conflict and he believes that the data from the 1987a supernova is more reliable.

He said, "I am not just sceptical but quite openly dismissive of any claims of superluminal neutrinos."

Which means he has closed his mind to new experiments and evidence. In a later post, he then links to a blog which talks about the Supernova experiment, but even that blog had the good sense to add this:

"*Addendum* There are of course loopholes to this argument, for instance there may be higher order quantum gravity effects which violate Lorentz invariance [3]. Either way the result will be hotly debated - is it an unknown systematic error or some exciting hint at new physics?"

Do you realize how silly you look when I point out that the OPERA experiment has five-sigma results and the supernova measurement doesn't come close to that? Moreover, lorentz-violating neutrino oscillations can trivially explain how tachyonic neutrinos are consistent with both experiments--there is not enough time in flight in the Earth experiment uon neutrinos to convert to the other types. Not so with neutrinos from the supernova, whose speed averages out through multiple oscillations to be approximately

the essential difference between religion and science is that religion puts articles of faith before observed data. Which is exactly what the post he was responding to was doing.

For God's sake (har), no. That's not what the initial post was doing.

Not all data is equal. I can set up an experiment where the data collected conclusively shows that gravity repeals two objects rather than attracts. It will be rightfully so met with incredulity, with most people choosing to ignore it outright. Why? Because I'm a nobody in the field of gravitational research, and it is far more likely that I screwed up my experiment than that I found a new interaction mode for gravity. In this case, a bad grounding caused my metal balls to be electrically charged with the same polarity. My data might be right, but the conclusion is still wrong.

Even superstars in applied Physics can screw up their experiments. What we're currently seeing is Science in action: one group publishes an experiment, and people are disagreeing with it, dissecting it, creating their own versions of the experiment, with everything being very noisy. People are drawing on past experiments with well verified data to figure out what the current experiment means, how it can be refined, changed and prodded at to confirm or refute the initial conclusion. When the dust has settled, a consensus will emerge that either yes, the experiment's data was not influenced by systemic factors outside of the proposed theory, and that yes, the new theory does a better job explaining the entire set of accumulated data and our general understanding of the universe, or it doesn't.

New experiments should never, ever be taken either at face value, or outside the context of the current knowledge of Physics. One of the fundamental axioms of Physics is that at the core, the laws of Physics don't change on us. Constants are constant. F=MA doesn't undergo decay. This means that if a new experiment contradicts the results of an existing, well-established experiment, it is absolutely right to first look for problems in the methodology and setup of the new experiment. Otherwise, you'd try to rediscover all rules of the new universe with each experiment.

TLDR:Not all data is created equal, and not all theories are created equal. Ergo, not all data gets the same attention, nor should it.

Don't you mean - 4 years?(1/40.0000 of 168000 light years) Which is such a long period it is very hard to put a correlation between those numbers. because it is 4 years +/- 2 years. But the fact that they were there before the light could now be taken with a different view.

Beside that, are all neutrino's equal?

And beisde that, maybe their speed goes closer to the light speed at higher distances. This is really stuff that is unknown.

No, sort of. There are three known "kinds" of neutrinos: electron, muon, and tauon. And they seem to randomly change from one kind to another. This is why I don't dismiss the possibility that neutrinos might travel faster than c. If they do, it wouldn't be the first completely bizarre thing about them.

Uh, just to be specific, you're talking about the chirality of neutrinos. The way you phrase it, it sounds like an electron is a type of neutrino. It isn't. There are electron neutrinos, but they have no charge. They are merely part of the same family of leptons as the electron, hence the name. You probably knew that, but I had to do a re-read to figure out that that's not necessarily what you meant.

1) They got a result that defies are current understanding2) The people performing the tests assume it's an experiment error, but can't find it3) The people performing the tests were like " Hey scientific community*, we know this can't be right, but we can't find out where the error is, how about a little help?4) The scinetific community is like " what about this this and this5) Those are great. we checked and no, no and no? here is the results6) Well, ceck all youtr quipement and try again7) OK, oh look the same result just better refined.

So keep an open mind. Not a 'Hey man, anything is possible." open mind, but a mind that looks at the actual evidence.

Remember, about 125 year ago, someone came up with ideas that where complete outside out understanding of the universe as we know it. If everyone just dismissed bohr, then where would we be?

Whether or not this is true, it is a great example of science and it' workings.

For the record, I am skeptical of the findings, but I expected the community to have found something wrong.

Neutrinos change around for reason we don't know either. So it's not like we complete understand them.

" (1) Hadn't there been something about the relativistic effects of the GPS satellites messing with the data?"(2) Hadn't they just swapped out their differentiators, possibly doing the calculations at the point of impact, instead of 20' up the cable, at the cable mount?"

Unlikely (but way more likely than FTL neutrinos). They check that stuff a lot, they know how to do the math... But they are still humans, so there can be a problem somewhere. Nobody was able to find it up to now, people are still trying.

"2nd Thermo is a mathematical law"

It is a mathematical consequence of some models of the universe. Other models don't bring it as a consequence. Remember, we don't know how the universe behaves, we just have clues.

"To put it shortly, if you can do FTL particles, then you can send information back in time."

I was corrected recently here on/. while saying that. Ends up that you can't keep current physics at all, so any prediction based on current physics (and yours is based on Relativity and Maxell laws) is not reliable.

"Moreover, sending information back in time itself violates the 2nd law of thermo."

Can you prove it? I'm trying to for a time, but it seems that it doesn't follow from the postulate of paradox-free time travel.

Or maybe some as-yet-undiscovered property of spacetime or the universe at the quantum level delays neutrinos over vast distances...

Unfortunately for us, replicating the experiment with a second team in a second location entirely from scratch will be extremely expensive, given that this CERN location used for the experiment is unique.

Unfortunately for us, replicating the experiment with a second team in a second location entirely from scratch will be extremely expensive, given that this CERN location used for the experiment is unique.

There are other long-baseline neutrino experiments out there, such as MINOS [fnal.gov].

MINOS as it now exists can only check the 730 km trip from CERN to Italy, not the 18-metre (60-light-nanosecond) trip across the iron "hadron stop" at the end of the decay tunnel at CERN, which may be at the heart of the result. This is because MINOS uses a matched near detector / far detector layout, whereas OPERA measures from the original protons (which are "upstream" from the hadron stop).

Maybe it's a matter of is zero the first number or is one, if the clock is starting when the neutrinos enter the hadron stop but the yardstick is measuring from the outside of the hadron stop, then the 60 nS difference would just about work out to the excepted speed of light.

Which would seem to imply that if there's an effect here, it should probably be related to neutrinos-through-matter vs neutrinos-through-vacuum. That skepticism is well advised, but it doesn't make it impossible.

And how much of a vacuum can you really get in this universe? With all the virtual particles popping in and out all the time. It seems you'd need to be as weakly interactive as a neutrino to avoid being slowed down just by spacetime and all it's particles kicking up all the time. Considering vacuum space is going to have something in it, I wouldn't be that amazed if neutrinos just travel at closer to actual C than light does.

Not really. Assuming an average of 1 proton per m^3 for the interstellar medium all the way, its less than 2.5*10^-6 kg/m^2. But then of course the interstellar medium may be quite a bit more dense. Even 6 orders of magnitude gives us only 1kg/m^2 of mass over the 168 000 ly.

My first thought was what if neutrinos do not interact with gravity at all? In this case spacetime would be flat for them and they would take the short straight line instead of following the curved spacetime. Unfortunately this would account for much less than the observed 60ns.

That is false; there is minimal interaction with matter. If muon neutrinos are tachyonic, lorentz-violating oscillations would be changing between type and the slower electron and tau neutrinos, giving an average speed of c. In the OPERA experiment, the flight time is too short for oscillations, and the imaginary mass of a tachyonic neutrino would mean it travels along a spacelike geodesic while in Earth's gravity field.

Seems even the OPERA people who first ran the test are skeptical, so you're in good company.:) I think everybody is doing a we're not sure what we've got, but SOMETHING is happening, lets figure it out.

Remember though, the team who have discovered this effect have pointed out as much, and are also still skeptics of their own results. I don't mean to sound unskeptical of the result, but I think it is possible that neutrinos can under differing circumstances travel at different speeds.

The new measurement is much more convincing than the previous one. The difference is the size of the proton bunches used to produce the neutrinos at CERN: in original measurement, the proton bunches where huge (milliseconds) compared to the claimed offset in the neutrino pulse (60 nanoseconds). This required a lot of knowledge about the shape of the proton bunches, and a lot of statistical fitting. The new analysis includes a special run with nanosecond-width proton bunches, widely separated from one another, so that each neutrino can be definitely associated with a particular proton bunch at CERN, with knowledge of the production time at the nanosecond level.

Personally, I'll still be skeptical until it's confirmed by an independent group, but the result is a lot more believable now.

About ten microseconds. Still huge compared to 60ns, though. On the other hand the luminosity was much higher than with the 1ns pulses in the recent experiment and so theS/N was higher. The new experiment rules out a bunch of error sources though, and the combination is pretty hard to argue with. I'll be skeptical of superluminality even when the result has been replicated elsewhere, but I will be expecting exciting new physics.

Has anyone explained why neutrinos have to have a single velocity yet? Pretty much all the commentary I am reading in these stories assume that a neutrino from one source is going to have the same velocity as a neutrino from another source.

The theory is that neutrinos are massless, and massless energy particles always travel at the speed of light (things like light and gravity. And neutrinos). Why is a slightly harder question, but essentially it comes down to "because they can."

I'm pretty sure that neutrino flavour oscillations (which have been observed - taus changing into muons and electrons) are only explainable within the current frame of particle physics if they do have mass.

I'm not an expert on theoretical physics but according to the Standrad Model, neutrinos were originally thought to be mass-less. But the in trying to detect solar neutrinos, Raymond Davis [wikipedia.org] could only detect 1/3 of the neutrinos predicted by the Standard Model. This lead to a puzzle known as the solar neutrino problem [wikipedia.org] as no one could find a fault with his experiments but they couldn't explain his curious results either. It wasn't until Masatoshi Koshiba [wikipedia.org] verified the same effect in a different experiment that scientists began to believe his results. The problem was the Standard Model was wrong. Neutrinos because they were massless should also be stateless. Subsequent experiments showed that solar neutrinos were not stateless as they oscillate into different types of
neutrinos. Thus they could not be massless. Davis and Koshiba shared part of the 2002 Nobel Prize for this discovery.

It's quite ingrained to think of neutrinos as being massless, which would give them a single velocity, that of light. That might not be helping.

Since at least two of the neutrino species apparently *aren't* massless, they then would certainly have a different, and slightly slower, velocity. But they're so light that that velocity would be somewhere up near the velocity of light - so while they won't have the same velocity, I imagine the spread will be fairly unimportant.

Muons "oscillate" from electron to muon to tau and back again (this is what OPERA was designed to measure). Supernova muons will have gone through all three phases many, many times. In the unlikely event that muon neutrinos do exceed c the behavior of supernova neutrinos could be explained if one of the other types travels slower than c so that the speed averages out to exactly c. This is also unlikely of course, but what's one more impossible thing before breakfast?

Yes... but maybe we missed them. Neutrinos are really hard to detect, let alone identify the source direction. Given a non-directional, not-very-strong pulse, possibly widely distributed in time, an unknown amount of time before the supernova, which we weren't expecting, would it really be surprising to have missed it?

If I remember it correctly, the neutrinos should arrive years, not months before the light. That can be explained by the fact that we just weren't looking years before the fact. I know, it is a quite weard explanation, for that to be true the neutrinos should travel on just this speed, not a lower one, but we do have weard data to fit.

That second experiment from Opera, with the short bursts just takes away all simple explanations for the result. We have now just the possiblity they corrected some delay wron

This is addressed in the paper. The 1987a neutrinos have energies in the 1-20 MeV range while the OPERA result is for neutrinos in the 3-100 GeV range. That is around three orders of magnitude higher than the 1987a result. Page 3 section 1 paragraph 3 covers this (for some reason Slashdot won't let me block quote it):http://arxiv.org/pdf/1109.4897v2 [arxiv.org]
Superluminal neutrinos must have energy dependent velocities.

According to the maths posted by someone else, we'd have expected the neutrino burst over three years before the light arrived. Did anyone see an unexplained neutrino burst on their detector some time in 1984?

Not in a supernova burst. The initial implosion is deep inside the neutron star, and there's a lot of matter shielding it. Light interacts with matter, so it gets delayed on its way out, but the neutrino burst from that initial implosion doesn't. The predicted delay was of the same order of magnitude as the delay seen in SN1987a.

Oh, come on, seriously? You're going to insist that we watch 5000 supernovas before you'll accept this as a valid point? A single carefully measured *truly independent* data point is more valuable than a thousand repetitions of the same experiment.

Or to put it another way: say you measure the voltage of a battery 100 times with a voltmeter, and measure 0 volts every time. I hook it to a light bulb and the bulb lights up. Are you going to insist that my single observation is useless, or is it possible your voltmeter is broken?

A supernova explodes from the inside - so the initial burst of photons and neutrinos from the supernova is shielded behind the rest of the neutron star. Light gets blocked, but neutrinos don't, so they get out first.

Of course, there is good reason to be skeptical of this claim. A post from Universe Today (http://www.universetoday.com/89933/special-relativity-may-answer-faster-than-light-neutrino-mystery/), seems to indicate that OPERA may not have taken certain things into account in their measurements. Something about the relativistic motion of the GPS clocks. I'm not a Physicist, so I won't claim to understand fully all of the data. but I agree that independent checks are crucial.

Absolutely. They're planning on rerunning the experiment again and loosening their dependence on GPS to test this. Another possible (and loosely related) contaminant that doesn't involve new physics is the different clock rate at the two labs coming from the different gravitational field strength. Personally I'd expect that to be pretty insignificant, but it has to be checked before we all go haywire shouting that neutrinos are propagating off the brane, or whatever.

Ummm, no? They didn't just use GPS clocks, they physically carried atomic clocks from one location to the other. Look up the actual science behind what they did, it's pretty interesting. Oh, and relativistic factors of GPS systems is pretty standard learning in basic science. Maybe there was a compounding effect that they missed... but I doubt it. That article is 100% pure speculation. And it's bullshit, quite frankly. Check out this: Ars [arstechnica.com] article for what the team did. (They also ran photons between the sites to check the time, in addition to GPS and portable atomic clocks.)

Whatever it is, I give them props for trying to solve this in the most honest, transparent way possible and remaining open to being wrong. They're exemplifying "good" scientific method and that makes them more credible to begin with.

While I want to think that we could be on the verge of some new physics discoveries... I have my doubts. It very likely could be that OPERA is still using a flawed method and thus seeing flawed results.

That being said, if and when other (independent) groups can verify this claim, that will be an exciting day.

1) Yes, it could, they've attempted to take that into account. The main error would be in the length of the neutrino pulse; a long pulse is easier to detect (I think ~2000 neutrinos, or perhaps even more) but it's hard to pin down a precise time. The repeat experiment used very short pulses, which are harder to detect (~20 neutrinos) but which yield much more precise timings.

2) All observations so far are suggesting that neutrinos have a positive mass (or, to be more picky, that at least two of the neutrino species have a positive mass) of the order of a tenth of an electron volt or less. (Also, I think it would involve an imaginary mass to move faster than light, at least if you want to stick within current relativity - this result would suggest we might not want to do that, though.)

3) Yes. For instance, if we're confined to a 3-brane -- basically, a three-dimensional sheet that we and everything around us is trapped on -- and neutrinos are allowed to leak slightly from the brane then little kinks and ripples in the brane will let them take short-cuts through the other seven spatial dimensions. Gravity can do the same, but the idea is that neutrinos would be more tightly trapped to the brane, while gravitons can roam freely.

It might have nothing to do with neutrinis at all but be more
general: the distance through matter could simply be smaller. Mass is known to change the metric, but maybe it does in a different way.
What would be nice to check is to compare the light and
neutrini speed through matter. Lets dig a tunnel through the
moon....

General Relativity is a classical theory, but the underlying nature of reality is quantum. So General Relativity, like Newton's theory of gravity, is an approximation of reality. Now, I'm not saying that the neutrinos went faster than light, however, perhaps this experiment has finally revealed a hole in General Relativity in the way the equations are applied to the timing of the event.

Yes, maybe. My (more or less) professional opinion is that the experiment almost certainly hasn't shown this, and instead it will either turn out to be experimental error or a *demonstration* of relativity (either special or general; both affect clock rates in ways that can be significant for this experiment), but yes, it could finally be some experimental evidence against relativity. And since you're quite right in saying that general relativity is definitely "wrong" in that it's not a fundamental theory and cannot be treated as such, this shouldn't be terrifying - just very exciting.

But I'll withhold judgment for a while - I'm very sceptical about these results.

It doesn't, it only appears to. Special relativity only requires that information (also mass, energy, etc.) can't travel faster than light. Quantum spooky-action-at-a-distance doesn't move any of those things, so the fact that it appears to happen instantaneously over arbitrarily large distances isn't a problem -- it doesn't violate relativity or causality.

OPERA shows light travels little bit slower than the fastest objects we've measured. A little while ago we heard that in galaxies far, far away, either the electric charge is larger, Plank's constant is smaller or the speed of light is smaller (http://slashdot.org/comments.pl?sid=2507746). If it's the speed of light that's smaller, the required slow-down is of the same order of magnitude as the factor by which photons are slower than neutrinos as observed by OPERA.

Here's my take. There's a field of undetected particles (dark matter?) that refract light a tiny bit, and this field was denser in the early universe. This field would not affect the apparent speed of light as an observer moves through it, just as (ignoring dispersion) light traveling through moving glass doesn't pick up the glass' motion vector (i.e. this wouldn't manifest itself as the Luminiferous aether, which is experimentally disproved). Light from the 1987A supernova would not be delayed too much relative to the neutrinos because most of the journey was through regions of space with low dark matter density.

There: three mysteries (dark matter, OPERA neutrinos and the fine structure "constant") all tied together with a bow on top. If you know more physics than I (honours undergrad) and you think I've missed something, please tear into this hypothesis, either here or on my blog: http://many-ideas.blogspot.com/2011/11/ftl-neutrinos-and-fine-structure.html [blogspot.com]. I look forward to hearing from you!

But we should also stop assuming that the theory of relativity is more reliable than it is or that our knowledge is anything other than incomplete and premature. I think it is only a matter of time until we something that can exceed C.

Nobody's going to can relativity on the basis of one experiement done at one facility, even if it's consistently repeatable. There's just too much chance that you overlooked something, no matter how careful you are (and OPERA, to their credit, have apparently been *very* careful). The problem is that there's no other facility that can do this experiment at the required precision, and with no idea as to what we're actually seeing, there's no way to design another experiment to get another look at it. The next big news will be when MINOS's upgrades come on line in 2012. Then we'll have independent confirmation (or not).

These browser release schedules are getting out of control. First, FireFox considered updating as often as once every 5 weeks. Now, Opera is going to top them by developing faster than light technology so they can post updates before their predecessors were released! (Side note: I'm now running Opera version 10,573 and it's great. I expect to be able to update to 10,574 yesterday.)